Heater circuit and control



July 12, 1932.

Filed April 2. 1950 2 Sheets-Sheet 1 INVENTOR FRED G.VON HOORN July 12,1932. F. G. VoN HOORN v 1,867,428

HEATER CIRCUIT ANDA CONTROL v Filed April 2, 1950 2 Sheets-Sheet aFly-3:7- Y 4/ I 5/ W, z/ {Z 7% i Z v 3 V T 67 q Z; T 7,2" l d9 70 E a 7/53 INVENTOR FRED c. vo- HOORN' WYA Wy 'v i225: ailorizeys 45 A {7 B 45?I I Patented July 12-," 1932 G. VON HOORN, 0F BRIDGEPCRT, CONNECTICUT,ASSIGNOR T0 TEE BRYANT ELEC- TRIO COMPANY, OF BRIDGEPORT, CONNECTICUT, ACORPCBATION OF CONNECTICUT HEATER CIRCUIT AND CONTRCL Application filedApril 2, 1936. Serial No. M1317.

This invention has to do with the control of electrical heating elementsand with a system including a two-part resistance unit and a switchsuitably connected to establish circuits for giving high, medium and lowdegrees of heating selectively, whether the current is obtained from atwo-wire feed line or from a three-wire line having a neutral Wire. Thethree-wire line may be either'a direct current line of the Edison type,an alternating current single phase line, or two phase lines and theneutral of an alternating current, three phase, four wire system. Asingle switch is provided, and with any of these types of feed andwithout change in the arrangement of the contacts or in the connectionsfrom the switch to the heater unit, the three degrees of heating and anopen circuit condition are obtained at will by putting the switch in itsdifferent positions.

In the drawings:

Figures 1, 2, 3 and 4 are diagrams of the connections establishedbetween a supply line and a two-part resistance by the different bladesof a switch in its-high, medium, low and cit positions respectively.

Figure 5 is a diagrammatic view of a transformer feeding a single phase,three-wire line.

. Figure 6 is a similar View representing either a generator or thesecondary winding of a so called star transformer feeding a three phase,four-wire line.

Figures 7 and 8 are views in elevation from opposite sides of a switcharranged to embody the invention.

Figure 9 is a plan View of the base of the same switch, only the fixedcontacts being in place.

The resistance unit has an intermediate connection point giving twoparts or resist ances A, B which are put in circuit in diilerent ways togive difierent degrees of heating, the common use being in an electricrange. The range as generally built and sold has a switch and "feed linebusesor other feed line connection means as parts of its structure, inaddition to the resistance unit, so

that it need only be connected with the feed wires to be operated.

In some districts the current is supplied by a three-wire line of whichone wire is at neutral potential. This may be an Edison threewiredirectcurrent system or the analogous alternating current line from asingle phase source, (see Fig. 5) the neutral 11 of which is obtained bytappingin at the mid-point 10 of the secondary winding of thetransformer. In other supply systems, three wires, including a neutralwire, are used at any one point but they are three of the four wires ofa three phase line leading from a generator or from the secondarywinding of a star or Y transformer (Figure 6). In that case the neutralwire 12 is connected to the neutral point 13 of the transformer and eachof the other three wires 14, 15, 16 is connected to a phase winding. Theyoltage between any two phase lines, e. g. 15, 16, is not the same asthat between a phase line and the neutral wire 12 but is of the order of1.7

times as great' When the neutral and two phase lines are used as a threewire supply at a particular point, there is a similarity to the singlephase three wire system but not an identity with it since in the latterthe voltage difference across the outside lines is twice the voltageacross one outside line and the neutral line 11, whereas in the fourwire, three phase system, that is not the case. Finally, there is thecommon two-wire system, either with direct or alternating cur-' rent,which is used in many cases as the supply for electric ranges. 1

The switch andtheconnections described below are such that an electricrange made in accordance with them may be used, without change in theswitch or in the connections be tween the resistance, the switch and theline terminals, regardless of which of the types of feed described aboveis used, the only change in any other part of the range being theaddition or removal or" a connection between two of the feed lineterminals to change from a three-wire feed to a two-wire or vice versa.Such ranges therefore may be used in dif ferent localities were thepower systems are difi'erent. The switch, which is the part requiringthe most processing, may be the same for all ranges and being thusstandardized may be manufactured with greater economy.

The switch shown here is of the three blade type and in its mechanicalconstruction may be of any known suitable type giving a rotation of thethree blades in unison in successive steps or quarterturns.

The upper blade or commutator 20 of the switch has three arms of equallength and at the level at which it turns are two fixed contacts 21, 22at adjacent quarter points about the base. The middle blade 30 has threeblades also, one of which, 31, is longer than the other two, 32, 33which are at right angles to it. Considered with reference to angularposition, this blade has its arm 31 on the side opposite from that armof the upper blade which is at right angles to the other two. There arethree fixed contacts at the middle level, including two, 34, 35, atadjacent quan ter points opposite the quarter points at which the upperfixed contacts are located, these two being long enough to engage eithera long or a short arm of the middle blade 30. The third, fixed contact36 at this level is beneath the upper contact 21 or, in other words, isat the same quarter point and is a short Contact, that is to say, it canbe engaged by the long arm 31 but not by the short arms 32, 33. The.lower blade 40 has two arms 41, 42 which are in line on a diameter ofthe blade and parallel to the two arms of each of the other blades thatare in line with each other. Co-acting with these arms 41, 42 are twodiametrically opposite fixed contacts 43, 44 both long enough to beengaged by either arm of the blade. The contact 43 is at the samequarter point as the middle contact 35, and the other lower contact 44is beneath the upper contact 22.

The upper blade controls some of theconnections between one end 45 ofthe resistance unit and one feed wire terminal while the lower bladecontrols altogether the connections between the other end 46 of theresistance and a second terminal. Themiddleblade has the control of theconnection between the intermediate point 47 of the resistance and athird terminal in addition to controlling the part ofthe connections,between the said one end of the resistance and the corresponding feedwire terminal, that are not controlled by the upper blade. "It will benoted from the description following that the middle blade acts to closea connection from the one terminal to the one end of the resistance 45only when the upper blade is in an open position and when the middleblade itself is not acting to-close a connection from "the intermediatepoint 47 of the resistance to the third ter- B by the line 50 while theother upper con- V tact 22 is connected to the bus C by the line 51. Theconductor 52 connects the contact 36 of the middle deck with the line50, hence with the same end 45 of the resistance B, and the middlecontact 34 is connected with the intermediate point 47 of the resistanceA by the line 53, the connection to the bus D being from the contact 35by way of the line 54. One

lower contact 43 is in connection with the outare mutually insulated andare spaced to turn at the levels of the fixed contacts. The latter aremounted on the switch base 62 around the well 63 in which the switchmovement, including the escapement for giving a snap action, is mounted.

The wall of the base is cut away at certain points to form ledges at thedesired three levels. A low ledge64 supports a strap 65 which extendsout fromthe ledge and is bent downwardly, and which carries the lowerfixed contact 44 at one end and a binding post 66 at the other end. Thebinding post scrveseither to connect directly to the feed line (as shownin Fig. 9) or, where a panel of buses is used, to a leader forming theconnection 56 to the bus E as described above and as illustrated inFigures 1 to 4. A ledge 67 at a higher level provides support for abinding post 68 connected directly with the contact 34 at the middlelevel and serving as a load terminal, being intended for the connection53 leading to the intermediate point" 47 of the resistance. Betweenthese two ledgesand on the top of the'base wall is secured a bindingpost 69 which has a curved extension 70 to the quarter point at one sideof it where the extension positions the contact 22, formed by its end,at the level of the upper deck, directly above the contact 44.

This binding post 69 is for, either the line 51 7 leading to the bus Cor a feed line wire itself.

On the other side of the base isa low ledge 71 on which is a bindingpost 72 integral with the lower contact 43, this binding post providinga terminal for the line 55 connectmiddle deck supports a binding post 74that is directly connectedyby a curved extension 75 to the middlecontact 35 thus located above the lower contact 43. Either the line 54from the bus D or the feed wire D itself is connected to this bindingpost 7 4 which may be referred to as a mid-connection as it is the pointof connection between the switch and the feed line that is the neutralin the three memes I wire supply. On the same ledge 73 is a bind ,shownin Figure 5, the busD is connected to the neutral wire and the buses Cand E to the outside wires. In that case, the positions of the switchblades and the difi'erent connections thereby brought about are as shownin Figures 1, 2, 3 and 4 respectively for high, mediumand low heatingand for the open circuit condition. For the high degree, the tworesistances are across the outside wires, the lower blade 4 0 connectingone outside wire to the outside end of the resistance A nection with theintermediate point of the resistance but that is not a material factorwith either an Edison or a single phase threewire supply since theneutral is not relied upon to determine the current flowing in eachresistance. In the next position of the switch, that is, with the bladesadvanced one quarter turn clockwise, the resistanceA is cut out by thelower blade 40 and the resistanceB is put across the outside line andthe neutral by reason of the connections from bus C to bus D through theupper blade to the resistance and thence through the middle blade. Thisis for medium heating.

Another turn of the blades gives the connections for low heating,putting the two resistances in series across one outside line and theneutral line. The lower blade connects the outside feed line E to theouter end of the resistance A while, the middle blade connects the outerend of the resistance B with the neutral line by way of the lines 50,52, 53 and bus D.

' A further. turn of the blades opens all ofthe connections to theresistance unit. It is to be noted that in this off position, all of theblades are disconnected from the live contacts 22, 35 and 44, thusgiving a complete three-pole break, a condition that is very desirable.

When the current is received from a threewire supply consisting of twophase lines and a neutral forming part'of a three phase four-wiresystem, no changes whatsoever are made in the switch or in theconnections from the switch to the resistance. The neutral feed wire 13'is connected with the bus D and the two phase wires (e. g. 14, 15 inFigure 6) are connect-ed respectively with the buses C and E. When theswitch blades are turned, the same connections are established, puttingboth resistances across the outside lines with a connection from theneutral line to the intermediate point for high heating, one resistancealone across one outside line and the neutral for medium heat, and bothresistances in series across the other outside line and the neutral forthe low degree of heating. As in the case of an Edison three-wire feedor a single phase three-wire feed, this arrangement gives a balancedload. 7 I

The connection from the neutral tothe intermediate point in the highheat position becomes important when the three Wires of a three phase,four-wire supply are used. That connection is the one established, bythe middle blade 30 in the position for high heat, from the neutral busD to the intermediate point 47 of the resistance. As said above, thevoltage across two phase wires is not twice the voltage between onephasewire and the neutral as in the Edison and the single phasethree-wire systems, With the intermediate point at the potential of theneutral wire, however, the voltage across each resistance is the phasevoltage so that the effect given is the same as having twice thatvoltage across the two resistances in sefrom the-switch to theresistances and to the buses, but provision is made to adapt the busesto the two feed wires. A short strap, indicated by the dotted line F inFigure 1, is added to connect the buses C and E. Then one feed wire isconnected to either of'these buses and the other feed wireis connectedto the bus D that serves as the neutral in the three-wire feed. Thatisiequivalent to connecting the upper contact 22 to the lower contact44. and feeding both from one supply wire or to connecting one side ofthe two-wire line to both terminals C, E.

The three degrees of heating are obtained in the same three positions ofthe switch blades. In the position shown in Figure 1, the tworesistances are put in parallel across its the-mains because theintermediate point is dle blade and the lines 52 and 50 between theswitch and the resistance.

As set forth ab0ve,.it is possible to con- 'nect the feed wires to busesforming part of the heater installation and to connect the switchcontacts 22, 35 and 44 with these buses. Instead of using buses, thebinding posts on the switch itself may be used as the connectionpointsfor the feed Wires. If desired other expedients may be adopted asthere are many available- The words feed wire terminals are used here todesignate generally the means for effecting the juncture between theswitch contacts and the feed wires, with no intent to put a limitationon the way the connection is brought about. For no other reason than togive it a name for more convenient reference, the feed wire terminalthat is at the neutral when a threev wire feed is employed and that isat the potential of one side of a two-wire line when that is used, isreferred to as the mid-terminal. In adapting the system to a twowirefeed, the connection F between feed wire terminals may be of any sortsuitable for establishing the potential of one side of the two-wire lineat the two terminals; or one of the two wires may be branched andconnected with both terminals. The changeover may, if desired, be madeby changes in the switch designed to connect the two contacts 22 and 44or their equivalents but that is not necessary.

I have used the term feeder in the appended claims with the intent thatthat term of the resistance to one feeder, a second blade arid contactscontrolling connections from another feeder to the midpoint and to theother end of the resistance, and closing a connection to the midpoint intwo consecutive on positions and to said other end in a third.onposition, the first blade 'being open in the second of'said consecutiveon positions, together with a third blade controlling connections fromsaid other end of the resistance to a third feeder, and closing aconnection in said two consecutive on positions and opening it in thethird on position, said switch having a spindle to which said blades areconnected and by which position, a second blade connecting the neutralwire only with the mid-point of the resistance in the high and mediumpositions and only with the said one end of the resistance in the lowposition, and a third blade connecting the other outside wire only withthe other end of the resistance in the high and low positions and notconnecting them in the medium position said switch having a spindle towhich said blades are connected and bydvhich they are rotatablesimultaneously.

3. A switch having three circuit closing positions for giving high,medium and low degrees of heating when controlling flow of current in atwo part resistance from a two- W1I'8 feed line, the said switch havingone blade connecting one side of the feed line to one end of theresistance in the high and medium positions and not connecting them inthe low position, a second blade conmeeting the other side of the lineonly with the mid-point of the resistance in the high and mediumpositions and only with the said one end of the resistance in the lowposition, and a third blade connecting the said one side of the linewith the other end of the resistance in the high and low positions andnot connecting them in the medium position said switch having a spindleto which said blades are connected and1 by which they are rotatablesimultaneous y.

In'testimony whereof I have signed my name to this specification.

FRED G. VON HOORN.

